REMOTE ACCESS IN LINUX SYSTEMS
By the end of this article, you should be able to:
i) Discuss different remote access programs: telnet, Remote Shell (rsh), OpenSSH, VNC,
Remote Access Systems
a) telnet:-
telnet is one of the earlier protocols developed for the Internet back in 1969. It was originally codified in RFC 15. To learn more, take a look at the Network Subsystem for Time Sharing Hosts memo.
telnet was not built with security in mind, the protocol is sent over the wire in plain text
b) Remote Shell (rsh):-
Remote Shell (rsh) was originally written for the BSD (Berkeley Software Distribution) system in 1983. rsh is a similar system to telnet. Like telnet, rsh is an insecure protocol, which is not encrypted and sends data in clear text.
c) Secure Shell:-
The Secure Shell (SSH) protocol was developed to overcome the security concerns of telnet and rsh. The most widely used version of the SSH protocol is OpenSSH. OpenSSH is built upon the concepts of symmetric and asymmetric encryption.
The multiple layers of the OpenSSH architecture handle different parts of connection.

d) Virtual Network Computing (VNC) Server:-
The Virtual Network Computing (VNC) server allows for cross-platform, graphical remote access. There are several implementations available; the current common version is tigervnc client and server. The server component has Xvnc (the main server for VNC and X), vncserver (Perl script to control Xvnc), vncpasswd (set and change vnc-only password), and vncconfig (configure and control a running Xvnc).